Traditionally, soap bars are stamped from extruded billets of material in order to achieve bars of an attractive and uniform appearance. Bar stamping may be accomplished using a pair of opposing die members which are physically brought together (i.e., in the compaction step) to stamp the bars.
Rather than pressing together opposing die members forming a single cavity, the die can be an extended die, having a plurality of cavities on the die. The length of the die (and die backplate) is in fact fixed by the length of the press against which the die and die plate are mounted. Since as a practical matter, the press is bought as a standard size piece from the supplier, the length of the press and of the die are fixed.
Until now, it has been believed that the die cavities must be molded or machined such that an imaginary line crossing across the horizontal x-axis of the die would also cut across the horizontal x-axis right in the center of each of the die cavities on the die. That is, each of the cavities have been machined or molded to lie next to the other with a small space between one cavity and the other.
The spacing between the die cavities has been believed to be especially critical because when a billet (a "log" refers to the long extruded pieces after extrusion before cutting; a billet refers to the pieces after cutting; and a bar refers to the piece after it has been stamped from the billet) of soap which is about to be stamped is placed between the dies, it has been believed that a minimum amount of soap (soap volume of billet) is required to fill out the cavities. If the cavities were too close together, it has been believed that the soap cavities would not fill up and that the billets thus made would be no good.
Indeed, if one looks at a typical specification sheet from Binacchi and Company, i.e., the company which makes the soap presses used in stamping (see Binacchi "USN" Soap Press Specification Sheet), it can be seen that "A" refers to spacing between bars and "B" refers to the width of the bar at the edges. According to the specification sheet, as B gets greater, (i.e., from B=0 to B=0 to 8 to B=8 to 15 etc.), the spacing between die cavities A must also be made greater. Thus, there is a clear teaching away from the manufacturer of the industry used press to move the spacing together.
On the other hand, while spacing cavities further apart has been desirable to ensure die cavities are completely filled, the additional area between cavities also means that there will be additional rework (i.e., the amount of soap not used to fill the cavities and which must be sent back into the soap plodder to be "reworked" before being recycled once more to the stamping machinery). Rework is also known in the art as "flash".
Any flash or rework which must be sent back to the plodder means that the plodder, which has limited capacity to begin with, must be fed less soap mixture coming from further upstream into the plodder and this in turn ultimately means the throughput of finished bars is lessened.
Unexpectedly, applicants have found that, if the die cavities/bars are angled so that the horizontal axis of the cavity or bar is angled away from the horizontal axis of the press onto which the die is mounted, it is possible (though not required) to increase the number of die cavities over a fixed length of press (i.e., by at least one).
Further, because the spacing between the die cavities is reduced, the amount of soap rework is significantly reduced (i.e., because more of the soap/billets are being stamped into bars). Moreover, applicants have found that the additional cavity (e.g., 5 cavities instead of 4 in the case of examples shown) is filled using the same volume of extruded billet. It was particularly surprising to find that one can reduce spacing between cavities and fill out an additional cavity using the same volume of soap.